Trends in Horseshoe Crab Abundance Along the Atlantic Coast

The status of the Horseshoe Crab Limulus polyphemus population along the Atlantic coast is of interest to a variety of different stakeholders.  Horseshoe crabs play an important role in marine and estuarine ecosystems, and their eggs are a critical food source for many migratory shorebirds. The species also serves as a primary bait source for other commercial fisheries and is the backbone of a major biomedical process.  In the 2013 Atlantic States Marine Fisheries Commission (ASMFC) stock assessment update, we used autoregressive integrated moving average (ARIMA) models to examine trends in fisheries independent surveys.  Current status was assessed as the probability of the terminal year of the abundance indices being below index based reference points.  These reference points equaled the 25^th percentile of the fitted ARIMA model values and the 1998 fitted value since this was the year when the ASMFC began active horseshoe crab management.  Probabilities of being below reference points were summarized regionally.  In general, abundance in the southeast and Delaware Bay regions is stable or increasing whereas abundance in the New York and New England regions is declining.  These results reinforce the importance of management, regulations, and monitoring on a regional or localized scale.